1. Field of the Invention
The present invention relates to a rotary valve for mixture gas injection control which controls the opening and closing of a communicating passage communicating between a combustion chamber and a chamber, in an assist gas fuel injection mechanism of a 2-cycle internal combustion engine, and more particularly, to a protective layer applied to the surface of the rotary valve.
2. Description of the Background Art
The assist gas system fuel injection mechanism is a mechanism in which a highly compressed gas is reserved in a chamber provided adjacent to a combustion chamber, and a fuel is injected by using the highly compressed gas as an assist gas for formation of a mixture gas and for pushing out the mixture gas. As such a mechanism, there is known, for example, the one disclosed in Japanese Patent Laid-open No. Hei 10-325323.
As to a mixture gas injection control rotary valve in an assist gas system fuel injection mechanism applied to a 2-cycle internal combustion engine, hitherto, clearance has been set by giving priority to securing of gas-tightness under the most severe conditions through taking into consideration temperature rise due to receiving of heat during operation, dynamic strains and accuracy in production. Therefore, the clearance is somewhat large, the gas-tightness is lowered under other operating conditions, and it is necessary to increase the quantity of the fuel injection assist gas, so that the system must be larger in size.
In producing the rotary valve, the shape must be determined by taking into account the thermal strain and dynamic strain under operation, so that it has not been easy to produce the rotary valve. Further, where inappropriate clearance is generated due to dispersion of products arising from production errors, there is a possibility of the occurrence of seizure and adhesion due to the contact between the housing and the valve body, so that it has been necessary to enhance the accuracy in production, leading to difficulties of production and higher cost.
One problem to be solved in an assist gas fuel injection mechanism for a 2-cycle internal combustion engine is to reduce as much as possible the clearance between the valve body and the housing of a rotary valve, to reduce leakage of an injection assist gas, and to contrive a reduction in size of the assist gas fuel injection mechanism.
Another problem to be solved in an assist gas fuel injection mechanism for a 2-cycle internal combustion engine is to eliminate the necessity of high-accuracy working for fitting of the valve body of the rotary valve to the housing, to ensure that a minimum necessary minute clearance can be spontaneously formed during test running, and to enable inexpensive provision of parts.
Still another problem to be solved in an assist gas fuel injection mechanism for a 2-cycle internal combustion engine is to ensure that high durability can be obtained even where foreign matter has come into a sliding portion of the valve body.
The present invention, which has solved the above-mentioned problems, relates to an assist gas fuel injection mechanism for a 2-cycle internal combustion engine comprising a chamber communicated to a combustion chamber through a communicating passage, a rotary valve provided in the communicating passage for controlling the opening and closing of the communicating passage, and a fuel injection device provided in the communicating passage between the rotary valve and the chamber, such that a highly compressed gas from the chamber and a fuel from the fuel injection device are mixed with each other and supplied to the combustion chamber through the communicating passage.
The present invention provides a protective layer on an outside surface of a valve body of the rotary valve by using a material which is softer than the valve body of the rotary valve and a housing of the rotary valve and which is susceptible to plastic deformation.
In the assist gas fuel injection mechanism for a 2-cycle internal combustion engine as set forth above, a resin coating having a self-lubricating property may be used as the protective layer. Alternatively, a plating with a metal inactive to the material of the housing of the rotary valve may be used as the protective layer. Also, a composite plating having a self-lubricating property may be used as the protective layer.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.